The present invention relates generally to fastener driving tools used for driving fasteners into workpieces, and specifically to fastener driving tools employing batteries for powering certain tool functions.
Conventional fastener driving tools feature a reciprocating driver blade which impacts a fastener fed to a nosepiece by a magazine. Typically, as exemplified in Nikolich U.S. Pat. No. Re. 32,452, Nikolich U.S. Pat. No. 4,522,162; Nikolich U.S. Pat. No. 4,483,474; Nikolich U.S. Pat. No. 4,403,722 and Wagdy U.S. Pat. No. 4,483,473; as well as U.S. Pat. Nos. 5,197,646 and 5,263,439, all of which are incorporated by reference, a combustion-powered, fastener-driving tool includes a combustion chamber, which is defined by a cylinder body and by a valve sleeve arranged for opening and closing the combustion chamber. Generally, similar combustion-powered, nail- and staple-driving tools are available commercially from ITW-Paslode (a unit of Illinois Tool Works Inc.) of Vernon Hills, Ill., under its IMPULSE trademark.
An advantage of such tools is that they are totally portable, and as such do not require a connection to a supply of electricity or pneumatic fluid power. Combustion from a self-contained xe2x80x9cenginexe2x80x9d provides the power needed to drive the fasteners. However, supplemental battery power is needed to operate ancillary tool systems, such as the spark generation, fan motor power, warning lights and other functions well known to skilled practitioners. In more recent models of such tools, a rechargeable battery is provided for supplying the required power.
One disadvantage of the stressful operational environment of such tools is that the tremendous force of combustion exerts significant vibration and/or gravitational (g) forces on the tool components, including the battery and its connection point to the tool, commonly known as a terminal block. In fact, it has been found that such tools generate internal forces of at least 100 g""s, and reaching in the range of 300-500 g""s. This level of vibration and shock forces is now known to cause movement of the battery relative to the terminal block to the extent that the electrical contact between the battery and the terminal block is temporarily interrupted during combustion events due to micro-arcing.
This interruption is almost imperceptible, lasting only in the range of a few milliseconds. However, the interruptions are significant to the extent that, over time, the repetitive micro-arcing has been found to cause oxidation corrosion of the interface contacts between the terminal block and the battery. Especially when the respective contact surfaces are made of Cuxe2x80x94Ni alloys, after prolonged use, the corrosion impairs tool performance due to insufficient power reaching the tool from the battery. Ultimately, a conductivity breach occurs.
Faced with this problem, tool users must clean the contacts of the terminal block and the battery to remove corrosion. While the battery is removable from the tool and as such accessible for cleaning, the terminal block is difficult to access without significant disassembly of the tool. Such disassembly by unskilled tool users can cause unwanted problems due to improper reassembly.
Another design objective of such combustion tools is that the battery/terminal module interface maintains adequate electrical conductivity in the face of the at least about 100 g""s to which such tools are subjected during combustion.
Still another design objective of the battery/terminal module interface of such tools is that the contact elements forming the interface are designed to accommodate the insertion and withdrawal of the battery from the tool without causing undue wear and tear on the contact elements.
Thus, there is a need for a combustion tool featuring a battery/terminal block interface which accommodates the micro-arcing without generating oxidation or other corrosion. There is also a need for a combustion tool featuring a battery/terminal block interface which can withstand at least about 100 g""s and maintains good conductivity without causing undue wear on the battery/terminal module contact elements.
The above-identified design considerations are addressed by the present battery/terminal module interface in which the contact elements are able to withstand at least about 100 g""s without generating corrosive oxidation. At the same time, conductivity is maintained and the cost of the contact interface elements is competitive with the conventional Cuxe2x80x94Ni contact interfaces.
More specifically, a fastener driving tool is provided including a housing defining a cavity for insertion of at least one battery, a battery configured for insertion into the cavity and having at least one battery contact element. A terminal module is disposed in the cavity, and is constructed and arranged for engaging the battery and making an electrical connection therewith, the module including at least one terminal contact element. At least one of the battery and terminal module contact elements incorporates a precious metal alloy and the other of the contact elements is conductive.
In another embodiment, the contact interface is configured for a smooth transition between the respective contact elements. Another feature of the present invention is that the contact interface is capable of withstanding at least about 100 g""s and maintaining contact without suffering from oxidation-type corrosion.